3 files changed, 24 insertions, 47 deletions

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 390bdab01c3c..9f1369fe0afb 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1387,8 +1387,8 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
         struct mm_struct *mm = vma->vm_mm;
         struct mm_walk walk = {};
         struct mempolicy *pol;
-        int n;
-        char buffer[50];
+        char buffer[64];
+        int nid;
 
         if (!mm)
                 return 0;
@@ -1404,10 +1404,8 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
         walk.mm = mm;
 
         pol = get_vma_policy(task, vma, vma->vm_start);
-        n = mpol_to_str(buffer, sizeof(buffer), pol);
+        mpol_to_str(buffer, sizeof(buffer), pol);
         mpol_cond_put(pol);
-        if (n < 0)
-                return n;
 
         seq_printf(m, "%08lx %s", vma->vm_start, buffer);
 
@@ -1460,9 +1458,9 @@ static int show_numa_map(struct seq_file *m, void *v, int is_pid)
         if (md->writeback)
                 seq_printf(m, " writeback=%lu", md->writeback);
 
-        for_each_node_state(n, N_MEMORY)
-                if (md->node[n])
-                        seq_printf(m, " N%d=%lu", n, md->node[n]);
+        for_each_node_state(nid, N_MEMORY)
+                if (md->node[nid])
+                        seq_printf(m, " N%d=%lu", nid, md->node[nid]);
 out:
         seq_putc(m, '\n');
 
diff --git a/include/linux/mempolicy.h b/include/linux/mempolicy.h
index ea4d2495c646..9fe426b30a41 100644
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -169,7 +169,7 @@ int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
 extern int mpol_parse_str(char *str, struct mempolicy **mpol);
 #endif
 
-extern int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
+extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);
 
 /* Check if a vma is migratable */
 static inline int vma_migratable(struct vm_area_struct *vma)
@@ -307,9 +307,8 @@ static inline int mpol_parse_str(char *str, struct mempolicy **mpol)
 }
 #endif
 
-static inline int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
+static inline void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
 {
-        return 0;
 }
 
 static inline int mpol_misplaced(struct page *page, struct vm_area_struct *vma,
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 71cb253368cb..260b8213a873 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2914,62 +2914,45 @@ out:
  * @maxlen:  length of @buffer
  * @pol:  pointer to mempolicy to be formatted
  *
- * Convert a mempolicy into a string.
- * Returns the number of characters in buffer (if positive)
- * or an error (negative)
+ * Convert @pol into a string.  If @buffer is too short, truncate the string.
+ * Recommend a @maxlen of at least 32 for the longest mode, "interleave", the
+ * longest flag, "relative", and to display at least a few node ids.
  */
-int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
+void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
 {
         char *p = buffer;
-        int l;
-        nodemask_t nodes;
-        unsigned short mode;
-        unsigned short flags = pol ? pol->flags : 0;
-
-        /*
-         * Sanity check:  room for longest mode, flag and some nodes
-         */
-        VM_BUG_ON(maxlen < strlen("interleave") + strlen("relative") + 16);
+        nodemask_t nodes = NODE_MASK_NONE;
+        unsigned short mode = MPOL_DEFAULT;
+        unsigned short flags = 0;
 
-        if (!pol || pol == &default_policy)
-                mode = MPOL_DEFAULT;
-        else
+        if (pol && pol != &default_policy) {
                 mode = pol->mode;
+                flags = pol->flags;
+        }
 
         switch (mode) {
         case MPOL_DEFAULT:
-                nodes_clear(nodes);
                 break;
-
         case MPOL_PREFERRED:
-                nodes_clear(nodes);
                 if (flags & MPOL_F_LOCAL)
                         mode = MPOL_LOCAL;
                 else
                         node_set(pol->v.preferred_node, nodes);
                 break;
-
         case MPOL_BIND:
-                /* Fall through */
         case MPOL_INTERLEAVE:
                 nodes = pol->v.nodes;
                 break;
-
         default:
-                return -EINVAL;
+                WARN_ON_ONCE(1);
+                snprintf(p, maxlen, "unknown");
+                return;
         }
 
-        l = strlen(policy_modes[mode]);
-        if (buffer + maxlen < p + l + 1)
-                return -ENOSPC;
-
-        strcpy(p, policy_modes[mode]);
-        p += l;
+        p += snprintf(p, maxlen, policy_modes[mode]);
 
         if (flags & MPOL_MODE_FLAGS) {
-                if (buffer + maxlen < p + 2)
-                        return -ENOSPC;
-                *p++ = '=';
+                p += snprintf(p, buffer + maxlen - p, "=");
 
                 /*
                  * Currently, the only defined flags are mutually exclusive
@@ -2981,10 +2964,7 @@ int mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol)
         }
 
         if (!nodes_empty(nodes)) {
-                if (buffer + maxlen < p + 2)
-                        return -ENOSPC;
-                *p++ = ':';
+                p += snprintf(p, buffer + maxlen - p, ":");
                 p += nodelist_scnprintf(p, buffer + maxlen - p, nodes);
         }
-        return p - buffer;
 }